It is up to you as the patentee to enforce the patent and to look out for any suspicion of infringement, namely someone making, using, selling or importing the invention without your permission. The Patent Office has no role beyond patent registration and will not police your patent for you.
As soon as a patent is applied for, goods should be marked accordingly, e.g. Patent Applied For. This is intended to warn off infringers and pre-empts any defence by an infringer of innocent infringement - such a defence can prevent you from claiming damages. When a patent has been granted, you should also quote the patent number and indicate on the product that the product is patented. The wording and number must be removed from the product if the application is refused or if the patent expires.
A UK patent is only valid domestically and, if you operate in a wider market, international patent protection will need to be considered. Commercially, international protection is normally a practical necessity.
Bear in mind, especially in cases of fast moving technology, the requirement to publish a patentable invention may make patenting an inappropriate route. In such a case, copyright protection and protection of confidential information may be more appropriate.